Generally, mortar is a kneaded mixture of a powder material containing cement or lime, and water as solvent, and it makes use of a curing reaction by hydration reaction. Hence, usually it is mixed with water immediately before use and applied, and the working time is very short after kneading with water, and it is used immediately after kneading.
As shown in patent document 1, a cement-free mortar is known, which is applied on the surface of ceramic structure or the like. The mortar in patent document 1 is composed of fine ceramic particles, water as solvent, and silica sol, but when the time passes after kneading, ceramic particles settle, and the viscosity is elevated gradually, and the coating performance declines, and it has been needed to apply immediately after kneading with solvent.
The refractory mortar disclosed in patent document 2 is characterized by corrosion resistance expressed by the amount of magnesium hydroxide, but settling or viscosity changes occur with the lapse of time.
Thus, the existing mortar must be kneaded with the solvent immediately before use, and the kneading job at the site of coating is needed, and it cannot be stored for a long time, and the kneaded portion must be used up at the site. Moreover, the refractory mortar generally tends to shrink by drying or firing after application, form fine cracks on the coating surface, or cause gaps.    [Patent document 1] Japanese Patent Application Laid-Open No. 2004-231506    [Patent document 2] Japanese Patent Application Laid-Open No. 1991-75275